Fe-Ni based alloy

ABSTRACT

A Fe-Ni based alloy consists essentially of Ni of 25% by weight to 55% by weight, C of 0.001% by weight to 0.1% by weight, at least one element selected from Group IVb elements and Group Vb elements, e.g., Nb, or Ta of 0.01% by weight to 6% weight, and the balance being Fe and unavoidable impurities. The Fe-Ni based alloy contains dispersed particles inclusive of a carbide in the substructure. The carbide is a carbide of the Group IVb element or the Group Vb element. Since the dispersed particle inclusive of the carbide are finely and uniformly present in the substructure, mechanical strength, heat resistance and, a performance of punching work are improved. Additionally, a quantity of gas release in a vacuum can be reduced.

TECHNICAL FIELD

The present invention relates to a Fe-Ni based alloy having a smallthermal expansion coefficient.

BACKGROUND ART

A Fe-Ni based alloy, e.g., 42 wt % Fe-Ni, 29 wt % Ni, 17 wt % Co-Fe hasbeen hitherto known as an alloy having a low thermal expansion. Thiskind of Fe-Ni based alloy has been used in industrial application fieldswhere a metallic material having a low thermal expansion coefficient,e.g., a material for a lead frame used for producing an integral circuitpackage or the like, a material for a part constituting a cathode raytube for a Braun tube, a material for a part constituting an electrontube, a sealing material are required.

Firstly, description will be provided below as to, e.g., a material fora part constituting a cathode ray tube. A plurality of electrodes forconverging or deviating an electron beam emitted from a cathode arearranged in the cathode ray tube. With respect to a material requiredfor constituting the electrodes, it is an essential condition that thematerial have a small thermal expansion coefficient in order to assurethat an electron beam is emitted without any undesirable disturbance dueto thermal expansion during the working of the cathode ray tube. Forthis reason, the foregoing kind of Fe-Ni based alloy is employed. Inaddition, with respect to a shadow mask to be arranged in the cathoderay tube, the same kind of Fe-Ni based alloy is employed for the samereason as mentioned above.

However, although a conventional Fe-Ni based alloy satisfactorily meetsthe requirement for a low thermal coefficient, it has the followingdrawbacks. Accordingly, many strong requests have been raised so as toobviate these drawbacks.

One of the drawbacks inherent to the conventional Fe-Ni based alloy isthat a bur having a high height results during a punching operationperformed by actuating a press machine. When a material having a burhaving a high height formed in a punching region is employed for a partconstituting a cathode ray tube, there arises a malfunction and electronbeam properties are adversely affected. This problem likewise appearswhen the foregoing kind of material is employed for a part constitutingan electron ray tube. In addition, in the case where this material isemployed for forming a lead frame, if a bur has a high height, thereappear problems that the number of bending the lead pin is reduced, andmoreover, a running life of a press die is shortened. Also with respectto the sealing material, when a bur is located, e.g., in the sealingregion, cracks readily extend from the sealing region, wherebyproperties of the part are affected adversely.

In recent years, as semiconductor elements are integrated at a higherdensity, it is increasingly required that each lead frame is designed tohave a thinner thickness while using a number of pins. In connectionwith the foregoing current status, a material for forming a lead frame,composed of the conventional Fe-Ni based alloy, has problems that a finepattern can not be formed with excellent reproductivity, and moreoverthe material has insufficient mechanical strength and heat resistance.Not only with the material for forming a lead frame but also with amaterial for forming a part constituting a cathode ray tube, when thematerial for forming a part constituting a cathode ray tube hasinsufficient mechanical strength and heat resistance, it is remarkablysoftened by heat treatment carried out before an assembling operation.This leads to problems that handling capability is degraded andundesirable deformation is liable to occur during the assemblingoperation.

Generally, the conventional Fe-Ni based alloy has a large quantity ofdissolved gas. For this reason, when it is employed as a material forforming a part constituting a cathode ray tube or a material for forminga part constituting an electron tube, there appear problems that aquantity of gas release in a vacuum is increased and a degree of vacuumin the cathode ray tube or the electron ray tube is lowered, resultingin properties of a products being degraded undesirably.

The present invention has been made with the foregoing background inmind.

An object of the present invention is to provide a Fe-Ni based alloywhich assures that mechanical strength, heat resistance and otherproperties are improved.

Other object of the present invention is to provide a Fe-Ni based alloyhaving excellent working properties such as a performance of punchingwork.

Another object of the present invention is to provide a Fe-Ni basedalloy which assures that a quantity of gas release in a vacuum is keptsmall.

DISCLOSURE OF THE INVENTION

According to the present invention, there is provided a Fe-Ni basedalloy which is characterized in that the Fe-Ni alloy contains Ni of 25%by weight to 55% by weight, C of 0.001% by weight to 0.1% by weight andat least one element of 0.01% by weight to 6% by weight selected fromGroup IVb elements and Group Vb elements and the balance issubstantially composed of Fe and unavoidable impurities. In addition,the Fe-Ni based alloy of the present invention is characterized in thatdispersed particles inclusive of carbide are contained in thesubstructure of the Fe-Ni based alloy.

The reason why a composition of the Fe-Ni based alloy of the presentinvention has been defined in the above-described manner will bedescribed in the following.

Nickel is an element which serves to reduce a thermal expansioncoefficient. The thermal expansion coefficient is increased either whena content of the nickel is less than 25% by weight or when it exceeds55% by weight, resulting in an effective feature, derived from the alloyhaving a low thermal expansion coefficient, being lost undesirably. Itis preferable that the content of Ni remains within the range of 36% byweight to 50% by weight.

A carbon finely and uniformly disperses in the substructure as a carbideor at least a part of one element selected from the Group IVb elementsand the Group Vb elements. As a result, mechanical strength and heatresistance can substantially be improved while an adequate performanceof punching work is given to the Fe-Ni based alloy. The carbon functionsas a deoxidizer agent when producing an ingot. In other words, acharacteristic of the present invention is that the carbon isintentionally added. According to the present invention, a content ofthe carbon is determined to remain within the range of 0.001% by weightto 0.1% by weight. If the carbon content is less than 0.001% by weight,strength and heat resistance fail to be improved satisfactorily, andsufficient deoxidation can not be achieved when raw materials for theFe-Ni based alloy are molten. On the contrary, if the carbon contentexceeds 0.1% by weight, the property of workability is degraded, andmoreover, mechanical strength is excessively increased, resulting in aperformance of pressing work for forming various kinds of parts to theirpredetermined contour being degraded remarkably. It is more preferablethat the carbon content is determined to remain with in the range of0.01% by weight to 0.05% by weight.

At least one element selected from the Group IVb elements and the GroupVb elements is precipitated or crystallized in the form of a singleelement, a compound such as a carbide, nitride or an intermetalliccompound of Fe, and it is present in the form of dispersed particles inthe substructure. Thus, mechanical strength and heat resistance can beimproved while an adequate performance of punching work is obtained. Inaddition, the foregoing element serves to fixate a dissolved gascomponent as a carbide or nitride so as to reduce a quantity of gasrelease in a vacuum. Especially, the Group IVb elements and the Group Vbelements are an element which is liable to be precipitated as a carbideor nitride. Since the aforementioned effect can remarkably be obtainedwhen one element selected especially from Nb and Ta is used as theforegoing element, it is desirable that the foregoing element is used.

A content of at least one element selected from the Group IVb elementsand the Group Vb elements is determined to remain within the range of0.001% by weight to 6% by weight. If the content of the foregoingelement is less than 0.01% by weight, the added element issolid-dissolved in a matrix, resulting in a quantity of dispersedparticles composed of carbide becoming short. Thus, mechanical strengthand heat resistance can not be improved sufficiently. Additionally, aquantity of gas release is undesirably increased. On the contrary, ifthe content of the foregoing element exceeds 6% by weight, a property ofworkability is degraded, and moreover, mechanical strength isexcessively increased, resulting in a property of press-working forforming various kinds of parts to their predetermined contour beingdegraded remarkably. It is more preferable that a content of at leastone kind of element selected from the Group IVb elements and the GroupVb elements is determined to remain within the range of 0.1% by weightto 3% by weight. With respect to the Group IVb elements and the Group Vbelements, a plurality of elements may be used. Alternatively, a singleelement may be used. In the case where a plurality of elements are used,the total content of these elements should be determined to remainwithin the aforementioned range.

In addition, in the Fe-Ni based alloy of the present invention, it ispreferable that a content of S as an impurity is less than 0.05% byweight. This is because if the content of sulfur exceeds 0.05% byweight, a quantity of gas release in a vacuum is increased. Advantageouseffects derived from the present invention are not adversely affectedeven when Mn, added as a deoxidizing agent is contained by a quantity ofnot more than 2% by weight, and moreover, impurities such as P, Si arecontained by a quantity of not more than about 0.1% by weight.

As described above, in the Fe-Ni based alloy of the present invention,dispersed particles inclusive of a carbide of the Group IVb elements andthe Group Vb elements are present in the substructure. Since the carbideis finely and uniformly dispersed in the substructure, mechanicalstrength, heat resistance, a performance of punching work and otherproperties of the Fe-Ni based alloy are improved effectively. In otherwords, an effect derived from dispersion can be improved further, andmoreover, mechanical strength can be improved by uniformly dispersingthe fine particles of a carbide in the substructure. In addition, sincedislocation at high temperatures is suppressed, heat resistance such assoftening can be improved. Additionally, since a performance of punchingwork is improved by the fine crystalline structure due to the dispersedparticles, the height of a bur can be reduced.

It is preferable that a size of the dispersed particle is not more than20 μm, and moreover, it is preferable that the dispersed particleshaving the foregoing size are present within the range of 1000particles/cm² to 100000 particles/cm². It is more preferable that thenumber of dispersed particles remains within the range of 5000particles/cm² to 100000 particles/cm². If a size of the dispersedparticle exceeds 20 μm, mechanical strength and heat resistance fail tobe sufficiently improved and a performance of punching work is degraded.As a result, there is a tendency that the height of a bur appearingaround a punched hole (hereinafter referred to as a hole bur) isincreased. It should be noted that a size of the dispersed particlewhich has been referred to herein designates a diameter of a smallestcircle in which the dispersed particle is included. When the number ofdispersed particles is smaller than 1000 particles/cm², mechanicalstrength and heat resistance fail to be sufficiently improved. Inaddition, there is a tendency that a performance of punching work isdegraded, the height of the hole bur is increased and a breakage anglebecomes small. On the contrary, if the number of dispersed particlesexceeds 100000 particles/cm², a performance of rolling work or the likeis degraded.

The Fe-Ni based alloy of the present invention is produced, e.g., by wayof the following steps.

First, alloy components satisfying the requirement for theaforementioned alloy composition are molten and cast within thetemperature range of 1400° C. to 1600° C. to produce an ingot.Subsequently, the ingot is subjected to hot forging and/or hot rollingwithin the temperature range of about 1000° C. to 1200° C. Thereafter,the resultant plate is repeatedly subjected to cold working at a workingrate of 30 to 80% as well as annealing for a period of time of fiveminutes to one hour at a temperature of about 800° C. to 1100° C. As aresult, a required Fe-Ni based alloy is obtained.

For example, in the case where the Fe-Ni based alloy is employed forforming a lead frame, the hot working and cold working are employed toproduce a sheet material having a predetermined thickness. Subsequently,the sheet is subjected to punching to form a lead frame having apredetermined contour. In the case where the Fe-Ni based alloy isemployed as a material for forming a part constituting a cathode raytube, the aforementioned operations are conducted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view for explaining an evaluation method of a performance ofpunching work.

FIG. 2 is a plan view of a lead frame of one embodiment where the Fe-Nibased alloy of the present invention is used, and

FIG. 3 is a plan view of a part constituting a cathode ray tube ofanother embodiment where the Fe-Ni based alloy of the present inventionis used.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described in detail which illustratepreferred embodiments of the present invention.

First, description will be made below with respect to examples of aFe-Ni based alloy of the present invention and results derived fromevaluation on these examples.

EXAMPLE 1 to 23

Alloy components each of which composition is shown in Table 1 weremolten at a temperature of about 1500° C. and each molten alloy was castto form ingots. Thereafter, each ingot was forged at a temperature of1000° C. to 1200° C. to produce a billet having dimensions of 150 mm×600mm×L.

Thereafter, each billet was subjected to hot rolling at a temperature of1000° C. to 1200° C. until its thickness was reduced to 3.5 mm.Subsequently, the plate was repeatedly subjected to cold rolling andannealing under conditions of about 950° C.×about 30 minutes until itsthickness was reduced to 0.3 mm. After the cold rolled sheet wasadditionally subjected to cold rolling to reduce its thickness to 0.15mm, it was annealed at a temperature of about 950° C. for about 30minutes, whereby a plate-shaped alloy sample was obtained.

A size and the number of particles dispersed within several visualfields in each plate-shaped alloy sample obtained in the above-describedmanner were measured based on structure photographs by a metallurgicalmicroscope having a magnification of 400. Results derived from themeasurement are shown in Table 2. It should be noted that the size ofparticles dispersed shown in the table is represented by an averagevalue. In addition, with respect to the respective plate-shaped alloysamples, the following properties were evaluated. These results areshown also in Table 2.

(1) Thermal expansion coefficient

Numerals in a column of thermal expansion coefficient show a thermalexpansion coefficient measured within the temperature range of 30° C. to300° C.

(2) Variation of hardness for heat treatment

Each plate-shaped sample was subjected to heat treatment at atemperature of 1050° C. for 10 minutes, and hardness before and afterthe heat treatment were measured.

(3) Performance of punching work

A punching operation was performed for each plate-shaped sample with theaid of a press machine so as to form a hole, and a height of a burappearing around the punched hole and a breakage angle were measuredbased on the sectional form.

(4) Property of gas release

A quantity of gas release in a vacuum of 10⁻⁷ Torr was measured withrespect to each plate-shaped sample.

(5) Speed of gas release

A speed of gas release in the vacuum of 10⁻⁷ Torr was measured withrespect to each plate-shaped sample.

Evaluation on the performance of punching work as mentioned in the (3)was carried out such that a height h of the bur 3 appearing around theend of a broken surface 1 was measured as a bur height and that an angleθ defined by the broken surface 1 of the punched part and a punchedsurface 2 of the same was measured as a breakage angle. The smaller thebreakage angle θ, the larger the height h of the bur 3. In addition, thebur 3 was liable to tilt toward the punched hole side, causing variousproblems.

Additionally, for the purpose of comparison with the present invention,plate-shaped samples were similarly produced, using a Fe-Ni based alloydeparting from the scope of the present invention (Comparative Examples1 to 6). The compositions of the samples are shown in Table 1.Evaluation was carried out on the respective plate-shaped samples in thesame manner as the aforementioned examples. The results are additionallyshown in Table 2.

As is apparent from the results shown in Table 2, the Fe-Ni based alloyin the examples have a low thermal coefficient but exhibit a highhardness. In addition, the hardness of each plate-shaped sample was fewreduced after completion of a heat treatment at a temperature of 1050°C., Additionally, the breakage angle recognized after completion of apunching operation was large, and moreover, the height h of the bur islow. In other words, the Fe-Ni based alloy of the present invention issuperior in a performance of punching work. A quantity of gas release ina vacuum is small.

As is apparent from the above description, in the case where the Fe-Nibased alloy of the present invention is employed for a materialrequiring a low thermal expansion coefficient such as a material forforming a lead frame, a material for forming a part constituting acathode ray tube, a material for forming a part constituting an electrontube, a sealing material, even if it is a thin plate, the requirementsfor mechanical strength, heat resistance and other properties can besatisfied and reproductivity of a shape can be improved. For example,when it is employed as a material for forming a lead frame, theabove-mentioned advantages are obtained and, moreover, the number ofbending a lead can be improved. When it is employed as a material forforming a part constituting a cathode ray tube, it becomes possible toprevent its electron beam properties from being adversely affected,whereby a performance of assembling operation can be improved.Additionally, since a quantity of gas release is reduced substantially,properties of each product can be improved.

Next, the present invention will be described below with respect to anembodiment wherein the Fe-Ni based alloy of the present invention isemployed for forming a lead frame.

First, the Fe-Ni based alloy in Example 2 was repeatedly subjected tocold rolling and annealing under conditions of 950° C.×about 30 minutesso as to produce a sheet having a thickness of 0.25 mm. Subsequently,the sheet of the Fe-Ni based alloy was subjected to punching to exhibita contour of the lead frame as shown in FIG. 2, whereby a required leadframe 11 was obtained.

For the purpose of comparison with the present invention, a lead framewas produced in the same manner as mentioned above using the Fe-Ni basedalloy in Comparative Example 1.

Then, a hardness of each lead frame produced in the above-describedmanner as well as a running life of a punching die (represented by thetotal number of punching operations practically performed) weremeasured. Hardness (Hv) was 203 and the total number of punchingoperations was 850×10³ with respect to the lead frame in ComparativeExample 1, while hardness (Hv) was 240 and the total number of punchingoperations 1300×10³ with respect to the lead frame in Example 2. Thismeans that mechanical strength and a performance of punching work wereimproved with respect to the lead frame in Example 2 compared with thoseof the lead frame in Comparative Example 1.

Next, the present invention will be described below with respect to anembodiment wherein the Fe-Ni based alloy of the present invention wasemployed as a material for forming a part constituting a cathode raytube.

First, the Fe-Ni based alloy in Example 1 was repeatedly subjected tocold rolling and annealing under conditions of about 950° C.×about 30minutes so as to produce a sheet having a thickness of 0.175 mm.Subsequently, the sheet of Fe-Ni based alloy was subjected to punchingto exhibit a contour of the part constituting a cathode ray tube asshown in FIG. 3, whereby a required part 12 for a cathode ray tube wasobtained.

For the purpose of comparison with the present invention, a partconstituting a cathode ray tube was produced using the Fe-Ni based alloyin Comparative Example 2.

A cathode ray tube was assembled using the part produced in theabove-described manner and a rate of rejection due to deformation of thepart was then measured. The rate of rejection was 0.6% with respect tothe part constituting a cathode ray tube in Comparative Example 2, whilethe rate of rejection was 0.04% with respect to the part constituting acathode ray tube in Example 1. This means that the rate of rejection dueto deformation of the part Example 1 was remarkably improved comparedwith the part constituting a cathode ray tube in Comparative Example 2.

INDUSTRIAL APPLICABILITY

As described above, the Fe-Ni based alloy of the present inventionassures that the requirement for a low thermal expansion coefficient issatisfied, it has a high hardness and excellent heat resistance, it issuperior in performance of punching work, and moreover, a quantity ofgas release in the vacuum is small. Owing to these advantages, thepresent invention can provide an alloy material preferably employablefor, e.g., a material for forming a lead frame and a material forforming a part constituting a cathode ray tube.

                                      TABLE 1                                     __________________________________________________________________________              ALLOY COMPOSITION                                                             Ni Nb Ta Zr Ti V  Hf C  S  Fe                                       __________________________________________________________________________    EXAMPLES                                                                      1         36.3                                                                             4.23                                                                             -- -- -- -- -- 0.007                                                                            0.001                                                                            BALANCE                                  2         41.7                                                                             2.03                                                                             -- -- -- -- -- 0.021                                                                            0.002                                                                            "                                        3         42.0                                                                             1.47                                                                             -- -- -- -- -- 0.018                                                                            0.001                                                                            "                                        4         41.1                                                                             0.47                                                                             -- -- -- -- -- 0.042                                                                            0.002                                                                            "                                        5         49.7                                                                             0.04                                                                             -- -- -- -- -- 0.092                                                                            0.002                                                                            "                                        6         36.4                                                                             -- 5.21                                                                             -- -- -- -- 0.031                                                                            0.001                                                                            "                                        7         41.3                                                                             -- 1.68                                                                             -- -- -- -- 0.030                                                                            0.001                                                                            "                                        8         50.1                                                                             -- 0.63                                                                             -- -- -- -- 0.074                                                                            0.004                                                                            "                                        9         35.8                                                                             -- -- 1.25                                                                             -- -- -- 0.024                                                                            0.002                                                                            "                                        10        42.4                                                                             -- -- 0.51                                                                             -- -- -- 0.055                                                                            0.004                                                                            "                                        11        49.6                                                                             -- -- 0.14                                                                             -- -- -- 0.012                                                                            0.002                                                                            "                                        12        41.5                                                                             -- -- -- 3.05                                                                             -- -- 0.014                                                                            0.002                                                                            "                                        13        42.0                                                                             -- -- -- 1.83                                                                             -- -- 0.018                                                                            0.001                                                                            "                                        14        35.7                                                                             -- -- -- 0.64                                                                             -- -- 0.062                                                                            0.003                                                                            "                                        15        36.3                                                                             -- -- -- -- 4.01                                                                             -- 0.012                                                                            0.002                                                                            "                                        16        42.0                                                                             -- -- -- -- 1.85                                                                             -- 0.006                                                                            0.002                                                                            "                                        17        50.0                                                                             -- -- -- -- 0.42                                                                             -- 0.071                                                                            0.002                                                                            "                                        18        36.6                                                                             -- -- -- -- -- 4.11                                                                             0.013                                                                            0.002                                                                            "                                        19        40.9                                                                             -- -- -- -- -- 2.12                                                                             0.014                                                                            0.001                                                                            "                                        20        49.3                                                                             -- -- -- -- -- 0.73                                                                             0.087                                                                            0.002                                                                            "                                        21        41.5                                                                             0.57                                                                             0.43                                                                             -- -- -- -- 0.011                                                                            0.001                                                                            "                                        22        36.4                                                                             1.15                                                                             -- -- 0.44                                                                             -- -- 0.023                                                                            0.002                                                                            "                                        23        50.5                                                                             -- -- 0.11                                                                             -- 1.35                                                                             -- 0.041                                                                            0.001                                                                            "                                        COMPARATIVE                                                                   EXAMPLES                                                                      1         42.1                                                                             -- -- -- -- -- -- 0.027                                                                            0.006                                                                            "                                        2         41.8                                                                             -- -- -- -- -- -- 0.18                                                                             0.005                                                                            "                                        3         36.3                                                                             -- -- -- -- -- -- 0.062                                                                            0.004                                                                            "                                        4         51.2                                                                             -- -- -- -- -- -- 0.041                                                                            0.007                                                                            "                                        5         41.8                                                                             7.43                                                                             -- -- -- -- -- 0.091                                                                            0.001                                                                            "                                        6         36.0                                                                             -- 4.32                                                                             3.40                                                                             -- -- -- 0.033                                                                            0.002                                                                            "                                        __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________              SIZE OF         THERMAL  HARDNESS (Hv)                                        DISPERSED                                                                             NUMBER OF                                                                             EXPANSION                                                                              BEFORE  AFTER                                        PARTICLES                                                                             DISPERSED                                                                             COEFFICIENT                                                                            HEAT    HEAT    HEIGHT OF                            (m)     PARTICLES                                                                             (× 10.sup.-7 /°C.)                                                        TREATMENT                                                                             TREATMENT                                                                             HOLE                       __________________________________________________________________________                                                       BUR                        EXAMPLES                                                                      1         7.3     23050   88.1     181     160     0˜1                  2         7.4     8150    51.1     167     147     0˜1                  3         6.8     6740    52.7     157     141     0˜2                  4         6.4     5300    50.6     155     142     0˜1                  5         5.3     3700    94.5     146     137     0˜3                  6         10.4    21070   89.2     173     156     0˜1                  7         8.3     4850    50.3     162     145     0˜1                  8         8.2     3960    95.7     148     139     0˜3                  9         9.0     13200   87.9     174     152     0˜1                  10        8.5     3680    50.9     147     141     0˜1                  11        7.4     2040    96.1     146     136     0˜3                  12        9.7     11400   50.1     164     148     0˜1                  13        8.6     7400    51.6     157     145     0˜2                  14        7.2     4300    87.5     151     142     0˜2                  15        10.7    23400   88.3     176     155     0˜1                  16        8.4     5300    49.9     146     132     0˜2                  17        8.2     3200    96.2     151     144     0˜1                  18        7.8     9460    87.7     147     140     0˜3                  19        7.9     6070    48.3     165     143     0˜3                  20        6.7     2860    95.9     143     138     0˜2                  21        9.2     7100    51.3     158     142     0˜2                  22        8.3     6700    89.0     162     147     0˜2                  23        10.2    5800    96.2     154     141     0˜3                  COMPARATIVE                                                                   EXAMPLES                                                                      1         31       970    45.7     140     112     3˜5                  2         33       840    46.2     144     110     3˜5                  3         29       910    84.3     142     114     3˜5                  4         27       930    94.2     145     110     3˜5                  5         (NO WORKING CONDUCTED)                                              6         (NO WORKING CONDUCTED)                                              __________________________________________________________________________                                        QUANTITY OF                                                                            SPEED OF                                                     BREAKAGE                                                                              GAS RELEASE                                                                            GAS RELEASE                                                  ANGLE   (Torr · cc)                                                                   (× 10.sup.-3 Torr                                                       · cc/sec ·                                                  g)                               __________________________________________________________________________                      EXAMPLES                                                                      1         15˜20                                                                           6.8      0.71                                               2         13˜20                                                                           8.7      0.68                                               3         12˜18                                                                           9.4      0.97                                               4         12˜20                                                                           11.3     1.04                                               5         11˜16                                                                           12.4     1.12                                               6         12˜20                                                                           9.7      0.69                                               7         11˜23                                                                           9.6      0.83                                               8         12˜17                                                                           10.7     1.02                                               9         14˜20                                                                           10.1     0.92                                               10        16˜19                                                                           11.2     1.11                                               11        12˜17                                                                           10.3     0.95                                               12        13˜21                                                                           9.8      0.91                                               13        12˜19                                                                           8.7      0.89                                               14        11˜17                                                                           10.0     1.03                                               15        12˜19                                                                           7.4      0.88                                               16        11˜15                                                                           8.5      0.98                                               17        12˜18                                                                           9.3      0.96                                               18        11˜18                                                                           9.3      0.83                                               19        13˜22                                                                           9.4      0.91                                               20        12˜16                                                                           10.5     0.97                                               21        12˜20                                                                           8.9      0.74                                               22        12˜19                                                                           8.5      0.82                                               23        11˜17                                                                           9.2      0.98                                               COMPARATIVE                                                                   EXAMPLES                                                                      1         10˜11                                                                           17.1     1.90                                               2         10˜12                                                                           19.1     1.95                                               3         10˜11                                                                           18.3     1.86                                               4         10˜11                                                                           19.7     1.94                                               5         (NO WORKING CONDUCTED)                                              6         (NO WORKING CONDUCTED)                            __________________________________________________________________________

What is claimed is:
 1. A Fe-Ni based alloy for use in a cathode ray tubeconsisting essentially of:25 to 55% by weight of Ni, 0.001 to 0.1% byweight of C and 0.1 to 6% by weight of at least one element selectedfrom the group consisting of Group IVb elements and Group Vb elements;and the balance being Fe and unavoidable impurities, wherein said alloyhas dispersed carbide particles in a substructure thereof within therange of 1000 to 100,000 particles/cm², with each of said dispersedcarbide particles having a size of not more than 20 μm.
 2. A Fe-Ni basedalloy as claimed in claim 1, wherein a carbide of said dispersed carbideparticles is at least one carbide selected from the group consisting ofcarbides of Group IVb elements and Group Vb elements.
 3. A Fe-Ni basedalloy as claimed in claim 1, wherein said at least one element selectedfrom the group consisting of Group IVb elements and Group Vb elements isat least one element selected from Nb and Ta.
 4. A part for a cathoderay tube comprising a Fe-Ni based alloy consisting essentially of Ni 25to 55% by weight, C 0.001 to 0.1% by weight, 0.1 to 6% by weight of atleast one element selected from the group consisting of Group IVbelements and Group Vb elements, and the balance being Fe and unavoidableimpurities;wherein said alloy has dispersed carbide particles in asubstructure thereof within the range of 1000 to 100,000 particles/cm²,with each of said dispersed carbide particles having a size of not morethan 20 μm.
 5. A Fe-Ni based alloy, for use in a cathode ray tube,consisting essentially of:20 to 55% by weight of Ni, 0.001 to 0.1% byweight of C, 0.1 to 6% by weight of at least one element selected fromthe group consisting of Group IVb elements and Group Vb elements, andthe balance of Fe and unavoidable impurities, wherein said Fe-Ni alloyhas dispersed carbide particles in a substructure thereof within therange of 1000 to 100,000 particles/cm², with each of said dispersedcarbide particles having a size of not more than 20 μm, a quantity ofgas release in a vacuum of 10⁻⁷ Torr of said Fe-Ni alloy is less than13×Torr cc and a speed of gas release in a vacuum of 10⁻⁷ Torr of saidFe-Ni alloy is less than 1.2×10⁻³ Torr.cc/sec.g.
 6. A part of a cathoderay tube, comprising a Fe-Ni based alloy consisting essentially of Ni 25to 55% by weight, C 0.001 to 0.1% by weight, 0.1 to 6% by weight of atleast one element selected from the group consisting of Group IVbelements and Group Vb elements, and the balance of Fe and unavoidableimpurities;wherein said alloy has dispersed carbide particles in thesubstructure thereof within the range of 1000 to 100,000 particles/cm²,with each of said dispersed carbide particles having a size of not morethan 20 μm, a quantity of gas released in a vacuum of 10⁻⁷ Torr of saidFe-Ni alloy is less than 13×Torr cc and a speed of gas release in avacuum of 10⁻⁷ Torr of said Fe-Ni alloy is less than 1.2×10⁻³Torr.cc/sec.g.